Flutter参数处理插件smart_arg的使用

Flutter参数处理插件smart_arg的使用

smart_arg 是一个用于解析命令行参数的插件，它通过注解的方式将参数存储在类中，从而实现静态类型检查和代码补全。以下是关于如何使用 smart_arg 的完整示例。

简单示例

import 'dart:io';

import 'package:smart_arg/smart_arg.dart';

// 引入reflectable生成的文件
import 'readme_example.reflectable.dart';

[@SmartArg](/user/SmartArg).reflectable
[@Parser](/user/Parser)(description: 'Hello World application')
class Args extends SmartArg {
  // 定义一个字符串类型的参数，并设置帮助信息和环境变量
  @StringArgument(
    help: 'Name of person to say hello to',
    environmentVariable: "GREETING_NAME",
  )
  String name = 'World'; // 默认值为 "World"

  // 定义另一个字符串类型的参数，并限制其取值范围
  @StringArgument(
    help: 'Message to say to person',
    mustBeOneOf: ['Hello', 'Goodbye'],
    environmentVariable: 'GREETING_TYPE',
  )
  String greeting = 'Hello'; // 默认值为 "Hello"

  // 定义一个整数类型的参数，并设置其为必填项，以及最小最大值
  @IntegerArgument(
    help: 'Number of times to greet the person',
    isRequired: true,
    minimum: 1,
    maximum: 100,
    environmentVariable: 'GREETING_COUNT',
  )
  late int count;

  // 定义一个帮助参数
  [@HelpArgument](/user/HelpArgument)()
  bool help = false;
}

void main(List<String> arguments) {
  initializeReflectable(); // 初始化reflectable

  var args = Args()..parse(arguments); // 解析命令行参数
  if (args.help) {
    print(args.usage()); // 打印帮助信息
    exit(0);
  }

  for (var i = 0; i < args.count; i++) {
    print('${args.greeting}, ${args.name}!'); // 输出问候语
  }
}

帮助输出

上述示例的帮助输出如下：

Hello World application
  --name         Name of person to say hello to
                 [Environment Variable: $GREETING_NAME]
  --greeting     Message to say to person
                 [Environment Variable: $GREETING_TYPE]
                 must be one of Hello, Goodbye
  --count        Number of times to greet the person
                 [REQUIRED]
                 [Environment Variable: $GREETING_COUNT]
  -h, --help, -? Show help

构建过程

smart_arg 依赖于 reflectable 包，因此需要在构建过程中添加相应的配置。你的 build.yaml 文件应类似于以下内容：

targets:
  $default:
    builders:
      reflectable:
        generate_for:
          - bin/main.dart

每次修改 SmartArg 类或执行程序前，必须运行以下命令来生成必要的反射代码：

$ pub run build_runner build

完整示例

以下是一个更复杂的示例，展示了如何使用 smart_arg 来处理多组参数和命令：

import 'dart:io';

import 'package:smart_arg/smart_arg.dart';

// 引入reflectable生成的文件
import 'command_example.reflectable.dart';

[@SmartArg](/user/SmartArg).reflectable
[@Parser](/user/Parser)(description: 'get file from remote server')
class GetCommand extends SmartArgCommand {
  [@BooleanArgument](/user/BooleanArgument)(help: 'Should the file be removed after downloaded?')
  bool? removeAfterGet;

  [@HelpArgument](/user/HelpArgument)()
  bool? help;

  [@override](/user/override)
  void execute(SmartArg parentArguments) {
    if (help == true) {
      print(usage());
      exit(0);
    }

    if ((parentArguments as Args).verbose == true) {
      print('Verbose is on');
    } else {
      print('Verbose is off');
    }

    print('Getting file...');

    if (removeAfterGet == true) {
      print('Removing file on remote server (not really)');
    }
  }
}

[@SmartArg](/user/SmartArg).reflectable
[@Parser](/user/Parser)(description: 'put file onto remote server')
class PutCommand extends SmartArgCommand {
  [@BooleanArgument](/user/BooleanArgument)(help: 'Should the file be removed locally after downloaded?')
  bool? removeAfterPut;

  [@HelpArgument](/user/HelpArgument)()
  bool? help;

  [@override](/user/override)
  void execute(SmartArg parentArguments) {
    if (help == true) {
      print(usage());
      exit(0);
    }

    if ((parentArguments as Args).verbose == true) {
      print('Verbose is on');
    } else {
      print('Verbose is off');
    }

    print('Putting file...');

    if (removeAfterPut == true) {
      print('Removing file on local disk (not really)');
    }
  }
}

[@SmartArg](/user/SmartArg).reflectable
[@Parser](/user/Parser)(
  description: 'Example using commands',
  extendedHelp: [
    ExtendedHelp('This is some text below the command listing',
        header: 'EXTENDED HELP')
  ],
)
class Args extends SmartArg {
  [@BooleanArgument](/user/BooleanArgument)(short: 'v', help: 'Verbose mode')
  bool? verbose;

  [@Command](/user/Command)(help: 'Get a file from the remote server')
  GetCommand? get;

  [@Command](/user/Command)(help: 'Put a file on the remote server')
  PutCommand? put;

  [@HelpArgument](/user/HelpArgument)()
  bool? help;
}

void main(List<String> arguments) {
  initializeReflectable();

  var args = Args()..parse(arguments);

  if (args.help == true) {
    print(args.usage());
    exit(0);
  }
}